After install MySQL4.0.21-nt, something was wrong (how to change back to mysqld ?)

If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Unanswered: After install MySQL4.0.21-nt, something was wrong (how to change back to mysqld ?)

I was using "MySQL 4.0.20-standard" version before, and everything was fine when developing application. Today after I clean install "MySQL 4.0.21-nt", there was an error message for my previous application:

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource .....You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax .....

I don't know if you guys met this problem before. What I should do next? How can I reload the standard windows server but not nt version? (under mysql/bin/, there are couple of differernt files like: mysqld-nt, mysqld etc.)